The published scientific information, for example, as in Zinsser's textbook of Bacteriology, reports Lacto bacillus acidophilus produces no infection in man through some investigators believe that it is of importance in the production of dental caries. Carious lesions of the teeth invariably contain lactic acid producing bacteria.
It is believed that food is trapped in interdental spaces from which it is difficult to remove it. Bacteria of all kinds are in the mouth at all times and these are deposited on these food debris pockets. Some of the bacteria are the lactic acid producing type. Since the food pocket is protected from saliva by its outside layers and the bacteria are anaerobic, acid is produced without dilution in proximity to the tooth surface. This acid can have a concentration which, over time, damages the protective tooth enamel. Once the enamel is penetrated further tooth damage occurs quickly by the acid and by other bacteria.
Brushing and flossing of teeth clean out the food and, if done well, will prevent or retard dental caries. Some toothpastes contain alkali to neutralise the acid. There is a recently developed chewing gum with acid neutralising constituents. All these things help to prevent tooth decay. Their success seems to indicate that the theory of dental caries production is correct as detailed above.
It seems probable that the initial damage to the teeth is caused solely by the acid producers and that the other bacteria are harmless until tooth enamel damage occurs.
A bacteriophage is a minute organism which is a virus. Each virus attacks specific bacteria and there are as many viruses (phages) as there are kinds of bacteria. The virus attaches itself to a bacteria cell and injects its own DNA into the bacteria. This replicates, using the proteins of the bacteria and, at a later stage, the bacteria cell bursts releasing many new phages which then attack other bacteria. Each kind of phage attacks only one kind of bacteria. In the case of the T.sub.2 bacterophage acting on a bacteria E. coli the above takes about 30 minutes after exposure of the bacteria to the virus and about 120 phage particles are freed for each bacteria cell attacked. The rapid growth in numbers of phages would obviously reduce the bacteria present in a small localised area to a small number in a matter of a few hours.
Bacteriophages are easily propagated in suitable cultures of the host organism. Studies of the T.sub.2 phage on E Coli showed that when the T.sub.2 phage was innoculated in liquid cultures in the ratio of 1 phage per 500 bacteria complete lysis (bursting of cells) occured in 8 hours. Using the T.sub.7 phage complete lysis occured in 2 hours. Titers indicated 10,000,000,000 phages per ml of liquid. The mass of phage recoverable from such purified preparations is about 5 to 15 milligrams per liter of culture. Hence the method of obtaining phages is well known and completely practical. Phages for prevention of clostridia in silage preparation have been made and sold commercially. The manufacturing methods are available in the prior art.